Throughout Advent, the Church prescribes readings from the greatest of the prophets, the Prophet Isaiah, whose writings foreshadow the birth, life, death, and resurrection of Jesus Christ.
On the first Sunday of Advent, we read the beginning of the book of Isaiah, where the prophet speaks in the voice of God and calls the people of Israel to repentance, to prepare them for the coming of His Son. But the Old Testament people of Israel also represents the New Testament Church, so the call to repentance applies to us as well. Christ has already come, at the first Christmas; but He is coming again at the end of time, and we need to prepare our souls.
We need to "cease doing evil, and learn to do good," and Isaiah mentions specific acts of charity that we might take to heart this Advent season: help those who are oppressed, by poverty or injustice; relieve the orphaned; care for widows. Our works flow from our faith, and are a sign of that faith. But, as the Apostle James declared, "Faith without works is dead."
Isaiah 1:1-18 (Douay-Rheims 1899 American Edition)
The vision of Isaias the son of Amos I which he saw concerning Juda and Jerusalem in the days of Ozias, Joathan, Achaz, and Ezechias, kings of Juda.
Hear, O ye heavens, and give ear, O earth, for the Lord hath spoken. I have brought up children, and exalted them: but they have despised me. The ox knoweth his owner, and the ass his master's crib: but Israel hath not known me, and my people hath not understood.
Woe to the sinful nation, a people laden with iniquity, a wicked seed, ungracious children: they have forsaken the Lord, they have blasphemed the Holy One of Israel, they are gone away backwards.
For what shall I strike you any more, you that increase transgression? the whole head is sick, and the whole heart is sad. From the sole of the foot unto the top of the head, there is no soundness therein: wounds and bruises and swelling sores: they are not bound up, nor dressed, nor fomented with oil.
Your land is desolate, your cities are burnt with fire: your country strangers devour before your face, and it shall be desolate as when wasted by enemies.
And the daughter of Sion shall be left as a covert in a vineyard, and as a lodge in a garden of cucumbers, and as a city that is laid waste. Except the Lord of hosts had left us seed, we had been as Sodom, and we should have been like to Gomorrha.
Hear the word of the Lord, ye rulers of Sodom, give ear to the law of our God, ye people of Gomorrha.
To what purpose do you offer me the multitude of your victims, saith the Lord? I am full, I desire not holocausts of rams, and fat of fatlings, and blood of calves, and lambs, and buck goats. When you came to appear before me, who required these things at your hands, that you should walk in my courts? Offer sacrifice no more in vain: incense is an abomination tome. The new moons, and the sabbaths, and other festivals I will not abide, your assemblies are wicked. My soul hateth your new moons, and your solemnities: they are become troublesome to me, I am weary of bearing them. And when you stretch forth your hands, I will turn away my eyes from you: and when you multiply prayer, I will not hear: for your hands are full of blood.
Wash yourselves, be clean, take away the evil of your devices from my eyes: cease to do perversely, learn to do well: seek judgment, relieve the oppressed, judge for the fatherless, defend the widow.
And then come, and accuse me, saith the Lord: if your sins be as scarlet, they shall be made as white as snow: and if they be red as crimson, they shall be white as wool.
- Source: Douay-Rheims 1899 American Edition of the Bible (in the public domain)